# Question about the current flow and voltages in a simple NAND diagram

I've so far learned about boolean algebra and its applications to transistors. This is a picture of a NAND diagram:

A NAND has this boolean property : $f(A,B) = \overline{A \cap B}$. What I want to know is how the current is flowing (increasing/decreasing) and the voltages across the collectors. For example, lets say a voltage is applied to A but not to B, then the output which is a load lights up. From my understanding, you need a high enough voltage applied to the base of of a transistor to turn it on and once the base is saturated, you'll have enough current flowing from the collector to emitter. The current on the collector decreases which should mean a low voltage reading on the collector, but this transistor is connected to another transistor. Why is B turned off creating this reading across the resistor?

• Is point B floating, or connected to 0V? Nov 29 '14 at 10:53